Method for preserving documents and the like



Patented Nov. 17, 1942 UNITED-STATES PATENT OFFICE.-

. 2.301.990 rmrnon roa msaavmc nocumz'ms William J. Barrow, Richmond, Va.

No Drawing. Application January 10, 1941,

Serial No. 374,006

(Cl. l2)

12 Claims. This invention relates to a method for preserving documents and other fibrous materials, particularly old documents or the like, and has special utility in preserving documents or the like which have become deteriorated by age, handling, etc. The present invention is thus available for the preservation of a wide variety of papers, parchments, leaves of books and pamphlets, newspapers, pictures, manuscripts, etc., as well as cloth and other fibrous materials, and in describing and claiming the invention as applied to documents" it is to be expressly understood that the term document is used in its broadest sense as generic to any of the'foregoing. This and complication in procedure that are disadvantaseous.

'It is an object of this invention to provide a method whereby the document may be supplied with a preservative coating meeting the requirements herein set forth by use of a single homogeneous film at one or both faces of the document and thereby avoid the expense and complication implicit in the use of separate adhesive and nonadhesive sheets or composite sheets composed of adhesive and nonadhesive layers at one or both faces of the document.

It has also been proposed heretofore, in the impregnation of articles with compositions comprising thermoplastic compounds, to preheat the material to which the thermoplastic material is to be applied and, in order to avoid deterioration of the materialto be coated or to improve the slow and expensive to carry out, involve costly equipment, and also present rather serious problems of obtaining uniform and permanent adherence between the document and its preservative coating.

It is an object of the present inventionto provide a method whereby more uniform and better adherencemay be eflected between the docu ment and'its preservative coating, and which also requires materially less expenditure of time and less expensive equipment.

It has also beenproposed heretofore 'tocoat p per or the like, on one or both faces, with a composite or laminated film which includes a layer of transparent or translucent thermoplastic adhesive on that side of the film which is to be applied to the paper or the like, as for example in the patents to Scott, Nos. 2,061,678 and 2,171,- 259, or with a film secured to the paper or the like by a separate layer or sheet of transparent or translucent thermoplastic adhesive, as for example in the patent to Walsh and Caprlo, No. 2,079,641. This use of an intermediate adhesive between the paper to be coated and the film which is to constitute the exposed suri'aceof the adhesion of the material thereto, to preliminarily treat said material to be coated, as for example in the patent to Schneider, No. 2,147,757.

It is an object of this invention to provide a method whereby a document to be preserved may be provided with a coating at one or both faces thereof without the expense and complication of pretreating the material to be coated.

Another object" of this invention is to provide a method of the type characterized which can be applied with equal facility to documents of various sizes, and can even be used for long elements such as rolls of parchment and the like.

.Another object of this invention is to provide a method of the type characterized which employs only simple and relatively inexpensive equipment.

Another object of this invention is to provide a method of the type characterized which can be carried out without necessitating that the document be retained in the equipment for long periods of time, so that successive documents may be rapidly treated in a single piece of equipment. Another object of this invention. is to provide a method of the type characterized which is expeditious in character so that a relatively large number of pages, sheets, or the like can be handied in a relatively short time. 1 Another object of this invention is to provide a method of the type characterized which assures uniform and permanent adherence between the document and its preservative coating.

Another object of this invention is to provide a method of the type characterized which avoids resulting structure involves. an increase in cost the dimculties heretofore encountered from the entrapment of air between the document and its a and its preservative coating, particularly at worn or thin places in the document.

Another object of this invention is to provide a method of the type characterized which avoids the difficulties heretofore encountered from "stickin of the preservative material to pressure applying elements when the coating has been applied under heat and pressure.

Another object of this invention is'to provide a method. of the type characterized which may be applied to badly deteriorated documents without injury to the surface material which is to be preserved. I r

Another object of this invention is to provide a method of the type characterized which may be used to supply new bodies for the surface portionsof documents that have become badly deteriorated, to the end that new and durable cores for the surface material may be supplied without in- Jury or defacement of the matter to be preserved,

Another object of this invention is to provide a method of the type characterized which is rela-' tively simple in nature, easy to perform and highly efficient in character.

Other objects will appear as the description of the invention proceeds.

The novel process of the present invention in- I volves, broadly stated, the application, to one or both faces of a document to be preserved, of a homogeneous film of thermoplastic material which is transparent or semitransparent, nonhygroscopic, tough and durable so as to withstand handling, resistant to microorganisms, air and hand transmitted chemical agents, insects. etc. Such athermoplastic film is composed of cellulose acetate provided with a suitable plasticizer or of other suitable cellulose derivatives,

such as ethyl cellulose, that are thermoplastic. The preferred preservative material is a foil or film of cellulose acetate of the acetone soluble variety plasticized with from twenty to fifty parts of cellulose acetate plasticizers such. for example, as dimethyl phthalate, diethyl phthalate, di-

v methoxy ethyl phthalate or triphenyl phosphate.

The novel procedure of the present invention will be exemplified by explaining in detail the treatment of a sheet of. paper which is to be provided with a preservative coating at both faces thereof, but as will be apparent to those skilled in the art the procedure thus explained may be applied to the protection of one face only of a document or to the preservation of other documents and other fibrous sheets. v

In its simplest form the method of this invention involves the application to each face of the document of a sheet, film or foil of thermoplastic cellulosederivative, such as the plasticized cellulose acetate above identified or its equivalent, said sheet, film or foil being of substantially uniform thickness and preferably larger than the document to be treated so as to overlap the edges thereof at one or more sides. Over each face of the document is then placed a sheet of flexible I and relatively nonporous andnon-thermoplastic material, such for example, as a sheet of tracing cloth or very dense paper, depending upon the finish desired, said sheet also being of such a character that it will not adhere to the cellulose derivative was to interfere with its being readily stripped therefrom without injury to the surface thereof. Preferably the sheets of tracing cloth or the like are made larger thanthe document coating sheet or sheets so that they overlap the same at all edges. Be-

asorooc cloth or the like is preferably, but not necestalcum powder to prevent sticking to the pressure applying elements, when using heat and pressure, as heretofore required with earlier procedures.

The composite assembly composed of the document with its coating and tracing cloth layers is then placed between two flexible plates. I have used brass plates of about $6 inch in thickness satisfactorily, butI prefer to use sheets of cardboard, such as cover boards for pamphlets, which are approximately .010 inch in thickness. This pair of flexible plates with the interposed composite sheet including the document to be pre served with its coating sheet or sheets and the tracing cloth. layers may for convenience be called a form.

This form is first heated in any suitable way.

preferably by placing the same between heated metal plates of any suitable character or construction to provide a prompt and substantially uniform heating of the form throughout. A pair of separable plates heated internally by electric resistance coils may be movably mounted for ready manipulation toward and away from each other on a single-frame. Using flexible plates ofthe character described I have found that heat on the order of from twenty seconds to two minutes in duration is ordinarily sufficient, but this will of course vary with the thickness and kind of material being treated and the temperature to which it is desirablethat the same be raised. In applying plasticized cellulose acetate coatings to the preservation of newspapers 1 have'found that a temperature of from 290 to 325 F. to be proper. A temperature above350 F. is undesirable as-likely to char. at least some papers. while the temperature should not be below 275 F. to obtain the desired penetration of the preservative material with the desired rapidity and completeness of bonding that is to be effected under pressure in the next step. Any

suitable heating means may be employed for the plates between whichthe form is disposed, and

if desired any suitable thermostatic control may sired temperature, it is at once subjected to suitv able pressure to'cause' the now thermoplastic preservative sheet or sheets to penetrate into and interlock with the surface fibers of the document.

andto this end it is subjected to pressure-applied progressivelyfrom one edge to the other so as-to exclude air ahead of the advancing pressure. The A cardboard or other flexible sheets of the form ap-' parently act as a cushion during the progressive tween the overlapping portions of the tracing 7 application of pressure from one edge to the other and therefore, notwithstanding thin spots inthe document, discontinuities and non-uniformity in the application. of the preservative material to the document are largely avoided. Any suitable means may be employed for applying'such progressive pressure. I preferably pass the form between rollers which may be mounted on the frame or the heating plates with their pass adiacent and in alignment with the space between a preliminary removal of the deteriorated fibers said plates when open, said rollers preferably being spring pressed to apply a definite and predetermined pressure per square inch to the form. The amount of pressure to be used will obviously vary. with the thickness and character of the document and the preservative layer 01 layers 7 is adequate, although under some circumstances pressures as high as 3,000 pounds per square inch may be necessary. With the rollers located on the same frame as the heating plates as above described the form, upon separation of the heating plates after heating, may be immediately passed between said rollers in a substantially straight line movement.

able foruse in treating another document.

The procedure as so far outlined assumes that a single sheet of cellulose derivative is applied to one or both faces of the document, but in some instances the thickness or condition of the document to be preserved is such that the resulting product would still be undesirably fragile. Whenever it is desirable that the document be simultaneously reenforced and strengthened as well as preserved a sheet of tissue paper or other transparent or semitransparent material may be applied to the exposed face of one or more of the sheets of cellulose derivative and adhered thereto simultaneously with the application of said cellulose derivative sheet or sheets to the docu ment. The tissue employed is preferably approximately .005 inchin thickness and composed of pure cellulose fibers. Such tissue not only reenforces the document but increases its tear resistance, its folding endurance and its capacity to withstand handling, while it leaves a surface appearance similar to paper.

If preferred a sheet of tissue having cellulose derivative applied at least to that face whichis to contact the document may be preliminarily prepared, or the tissue may have cellulose derivative on both faces thereof. Also in a suitable case a laminatedsheet composed of a larger number of layers of tissue and cellulose derivative may be used.

The present invention also provides a procedure which may be readily used when a document has become badly deteriorated to provide a new core therefor. To this end the document with its preservative coating applied as heretofore explained may be trimmed to the edgesof the document and the coating sheets stripped apart splitting the original paper in its own plane and leaving the surface fibers thereof embedded in the coating layers. These separated sheets may then be secured in any suitable way to a new body or core either with or without that are not embedded in the preservative coatings. Or the preservative coatings with the fibers embedded therein may be soaked and scraped to remove fibers not embedded in the coatings, after. which the preservative coatings may be-mounted in any suitable way upon a new paper or other suitable core, which may itself be impregnated with the cellulose derivative, or a sheet of cellulose -derivative may be interposed between the new body and the layer or layers carrying the surface fibers of the old document. Any other suitable procedure for removing the deteriorated fibers not embedded in the preservative coating sheet or sheets may be used, such as applying cellulose derivativesheets to the exposed fibers and again splitting as above outlined, a procedure that. may be followed one or more'times until a the desired fibers have been removed.

its

In place of using tissue paper as a reenforcement, as above indicated, any other suitable transparent reenforcing material may be employed by using the procedure heretofore outlined.

It will therefore be perceived that the procedure herein described effects a more uniform and permanent adherence of a preservative coat ing to a document or the like while involving much less expenditure of time and less expensive equipment. The method is' simple in nature easy and expeditious in performance, and readily adaptable to documents of various character including rolls as well as sheets. The document or the like is provided with an airproof coating which will enable handling without injury, and this is accomplished without the disadvantages of applying an adhesive between the document and its coating or using a, specially prepared laminated coating sheet. The method of .this

invention does not require that any portion of the equipment be withheld fromservice for long periods of time, and therefore the same equipment may. be used over and over again in the interest of economy. The method also avoids the dimculties heretofore encountered from air being entrappedbetween the document and its preservative coating, and uniform adherence is obtained even though portions'of the document may be of different thickness. Also the difilculties heretofore encountered in-avoiding sticking of the coating layers to the pressure applying elements, with resultant danger of injury to the document, have been overcome. The present invention also enables the surface portions of badly deteriorated documents to be transferred to new body members to preserve allmaterial at the surface thereof without injury or defacement thereof.

While the foregoing procedure has been described with considerable particularity it is to be expressly understood that the present invention, as will now be apparent to those skilled in the art, may be variously applied without departing from the spirit of this invention, and certain portions of the procedure above described may be used without other porticns thereof. Therefore reference is to be .had to the appended claims for adefinitlon of the invention.

What is claimed is:

1. A method of preserving documents and the like which includes the steps of applying a homogeneous protective sheet of thermoplastic cellulose derivative without an' interposed adhesive directly to the face to be preserved, assembling the compositeassembly so formed to a temperature that will produce penetration of the cellulose derivative of said protective sheet into the fibers of the document when subjected to pressure, and then progressively applying pressure from one edge to the other of the heated composite assembly so formed to progressively exclude air and effect a substantially uniform penetration of the cellulose derivative of said protective sheet into at least the surface fibers of the document. 2. A method of preserving documents and the like which includes the steps of applying a homo geneous protective sheet of thermoplastic cenu lose derivative without an interposed adhesive directly to the face to be preserved, assembling the composite sheet so formed between flexible sheets which are non-adherent to the protective sheet to provide a composite assembly, heating the composite assembly so formed to a temperature-that will produce penetration of the cellulose derivative of said protective sheet into the fibers f the document when subjected to pressure, then progressively applying pressure from one edge to .the other of the heated composite assembly so formed to progressively exclude air and effect a substantially uniform penetration of the cellulose derivative of said protective sheet into at least the surface fibers of the document, and then at once removing all of said pressure and said fiexible sheets and exposing the coated document to the air for cooling.

3. -A method of preserving documents and the like which includes the steps of applying a homogeneous-protective sheet of thermoplastic cellulose derivative without an interposed adhesive directly to the face to be preserved, applying to the outer face of each cellulosic sheet a sheet of flexible material that will notadh'ere thereto, heating the composite-assembly so formed to a temperature that will produce penetration of the cellulose derivative of said protective sheet into the fibers of the document when subjected to pressure, then progressively applying pressure from one edge to the other of the heated com posite assembly so formed to progressively exclude air and effect a substantially uniform penetration of the cellulose derivative of said protective sheet into at least the surface fibers of,the

document, and then at once removing all of said mogeneous protective sheet of thermoplastic cellulose derivative without an interposed adhesive directly to the face to be preserved, applying to I the outer face of each cellulosic sheet a sheet of flexible material that will notadhere thereto and a superposed exterior flexible sheet, heat ing the composite assembly so formed to a temperature that will produce penetration of the cellulose derivative of said protective sheet into the fibers of the document when subjected to pressure, then progressively applying pressure from one edge to the other of the heated composite assembly so formed toprogressively exclude air and effect a substantially uniform penetration of the cellulose derivative of said protective sheet into at least the surface fibers of the document, and then at once removing all of said pressure and exposing the coated document to the air for cooling. p

6. A method of preserving documents and the like which includes the steps of applying a homogeneous protective sheet of thermoplastic cellulose derivative without an interposed adhesive directly to the face to be preserved, applying to the outer face of each cellulosic sheet a sheet of flexible material that will not adhere thereto and a superposed exterior flexible sheet, heating the composite assembly so formed to a temperature that will produce penetration of the cellulose derivative of said protective sheet into the fibers of the document when subjected to pressure, then progressively applying pressure from one edge to the other of the heated composite assembly so formed to progressively exclude air and effect a substantially uniform penetration of the cellulose derivative of said protective sheet 7 into at least the surface'flbersof the document,

then at once removing all of said pressure and exposing the'coated document to the air for cool- 7. LA'I nethOd ofpreserving documents and the like which includes the steps of applying a ho-' mogeneous protective sheet of thermoplastic cel-' lulose derivative without an interposed adhesive directly to the face to be preserved, applying to the exposed face of said protective sheet an at pressure/and exposing the coated document to.

the air forcoolingv g 4. A method'of preserving documents and the likewhich includes thesteps of applying aihomogeneous protective sheet of thermoplastic cellulose derivative without an interposed adhesive 7.

least semitransparent reenforcing sheet of tis-' sue, assembling said sheets between flexible sheets,

heating the composite assembly so formed toa temperature that will producepenetration of the celluloseiqderivative of said i protective sheet into the fibers gofthe document when subjected to directly to the face to be preserved, applying a sheet of tracing cloth to the outer face of each cellulosic sheet, heating thecomposite-assembly so formed to a temperature that willproduce penetration of the cellulose derivative of said protective sheet into the fibers oi. the document 7 pressure,g and then progressively applying presjjsure'from one .edge to the other .of the heated composite assembly so formed to progressively exclude alr'and eflect a substantially uniform penetration of the cellulose derivative of said pmwhen subjected to pressure, then progressively applying pressure from one edge to the other of r the heated composite assembly so formed to pro! gressively exclude air and effect a substantially,

uniform penetration of the cellulose derivative of said protective sheet into at least the surface fibers of the document, and then at once removing all of said pressure and said tracing cloth cooling.

5. A method of preserving documents and the tective, sheet into at least the surface the document.

8. A method of preserving documents and the fibers of like which includes the steps of applying a homogeneous protective sheet'of thermoplastic cellulose derivative withoutan interposed adhesive directly to the face to be preserved, applying to the exposed face of said protective sheet an at and exposing the coated document to the air for least'semitransparent reenforcing sheet of tissue;-assembling said sheets between flexible sheets, heating the composite assembly soformed to a temperature that will produce penetration'of the cellulose derivative of said protective sheet into the fibers of. the document when subjected to pressure, then progressively applying pressure from one edge to the other of the heated coma I posite assembly so formed to progressively exclude air and effect a substantially uniform penetration of, the cellulose derivative of said protective sheet into at least the surface fibers of the document, and then at once removing all of said 5 pressure and said sheets and exposing the coated document to the air for cooling.

9. A method of preserving documents and the like which includes the steps of applying 'a homogeneous protective sheet of thermoplastic cellulose derivative without aninterposed adhesive directly to the face to be preserved, applying to theexposed face of said protective sheet an at least semitransparent reenforcing sheet of tissue, applying to the outer face of said sheet a sheet of flexible material that will not adhere thereto, heating thecomposite assembly so formed to a temperature that will produce penetration of the cellulose derivative of said protective sheet into the fibers of the document when subjected to pressure, then progressively applying pressure from one edge to the other of the heated com posite assembly so formed to progressively exclude air and effect a substantially uniform penetration of the cellulose derivative of said protective sheet into at least the surface fibers of. the document, and then at once removing all of said pressure and exposing the coated document to theair for cooling.

10. A method of preserving documents and the like which includes the steps of applying a homogeneous protective sheet of thermoplastic cellulosederivative without an interposed adhesive directlyto the face to bepreserved, applying to the exposed face of said protective sheet an at least semitransparentreenforcing sheet of tissue,

applying a sheet, of tracing cloth to the outer.

cloth and exposing the coated document to the air for cooling. t

t 11. A method of preserving documents and the a like which includes thestepsof applying a homogeneous protective sheet of thermoplastic cellulose derivative without an interposed adhesive directly to the face to be preserved, applying to the exposed face of said-protective sheet at an least semitransparent reenforcing sheet of tissue, applying to the outer face of said sheet a sheet of flexible material that will not adhere thereto and a superposed exterior flexible sheet, heating the composite assembly so formed to a temperature that will produce penetration of the cellulose derivative of said protective sheet into the fibers of the document when subjected to pressure, then progressively applying pressure from into at least the surfacefibers of the document,

and then at once removing all of said pressure and exposing the coated document to the air for cooling. 1

12. A method of preserving documents and the like which includes the steps of applying a homogeneous protective sheet of thermoplastic cellulose derivative without an interposed. adhesive directly to-the face to be preserved, applying to the exposed face of said protective sheet an at leastsemitransparent reenfor'cing sheet of tissue, applying to the outer face of said sheet of flexible material that will not adhere thereto and a superposed exterior fiexiblesheet, heating the composite assembly so formed to a temperature that will produce penetration of the cellulose derivative of said protective sheet into the fibers of the document when subjected to pressure, then progressively, applying pressure from one edge to the other of the heated composite assembly so formed to progressively exclude air and efiect a substantially uniform penetration of the cellulose derivative of said protective sheet into as least the surface fibers of the document,

then at once removing all of said pressure and exposing the coated document to the air for cooling, splitting the preserved document in its own plane, and mounting the face portion thereof with its preservative coating on a new base.

wniuAM J. BARROW. 

